Abstract
Infrared powder-absorption spectra of nine natural and five synthetic olivine samples across the forsterite–fayalite join have been investigated at room temperature in the range 70–1400 cm−1. Variations of peak positions as a function of Fe content are close to linear for those vibrational bands whose trend could be followed across the solid solution. Line-broadening has been quantified by autocorrelation analysis. Positive deviations from linearity of the line-broadening parameter, Δcorr, for groups of bands at low energies are consistent with the existence of local elastic strain heterogeneities at intermediate compositions in the solid solution. It also appears that the structure of forsterite is more homogeneous than Fe-rich olivines in relation to local elastic strain effects. Positive deviations from linearity of the line-broadening parameter for the low-energy regions scale linearly with calorimetric data for the enthalpy of mixing. This close correlation between line-broadening in IR spectra and calorimetric enthalpies of mixing has now been observed for four different binary solid solutions, and there is a further, qualitative correlation with bulk modulus.
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Acknowledgments.
The authors thank Dr. C. Francis, Harvard Mineralogical Museum, Prof. F. Caucia and Prof. R. Vannucci for providing natural samples. Prof. H. Kroll is thanked for kindly donating synthetic Fo30, Fo50 and Fo75 samples. Critical review by C.A. Geiger helped to improve the manuscript. Dr. M. Zhang provided invaluable assistance for the IR experiments. Dr. S. Reed is thanked for microprobe analyses. Financial support was provided by the Italian MURST Cofin Project 2001 Structural evolution and phase transition in minerals vs. temperature, pressure and composition.
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Tarantino, S., Carpenter, M. & Domeneghetti, M. Strain and local heterogeneity in the forsterite–fayalite solid solution. Phys Chem Minerals 30, 495–502 (2003). https://doi.org/10.1007/s00269-003-0357-8
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DOI: https://doi.org/10.1007/s00269-003-0357-8